diff --git a/Spanner/src/Operation.php b/Spanner/src/Operation.php
index 4740e82985d8..16c1f0aaf12f 100644
--- a/Spanner/src/Operation.php
+++ b/Spanner/src/Operation.php
@@ -1005,8 +1005,12 @@ private function formatPartitionQueryOptions(array $args): array
         $parameters = $args['parameters'] ?? [];
         $types = $args['types'] ?? [];
 
-        $paramsAndParamTypes = $this->mapper->formatParamsForExecuteSql($parameters, $types);
-        return $this->formatSqlParams($paramsAndParamTypes);
+        /** @var array{params: array, paramTypes: array} $paramsAndParamTypes */
+        $paramsAndParamTypes = $this->formatSqlParams(
+            $this->mapper->formatParamsForExecuteSql($parameters, $types)
+        );
+
+        return $paramsAndParamTypes;
     }
 
     /**
diff --git a/Spanner/src/ValueMapper.php b/Spanner/src/ValueMapper.php
index 636d84b26cde..93344374bbec 100644
--- a/Spanner/src/ValueMapper.php
+++ b/Spanner/src/ValueMapper.php
@@ -137,7 +137,7 @@ public function __construct(bool $returnInt64AsObject)
      *
      * @param array $parameters The key/value parameters.
      * @param array $types The types of values.
-     * @return array An associative array containing params and paramTypes.
+     * @return array{params: array, paramTypes: array}
      */
     public function formatParamsForExecuteSql(array $parameters, array $types = []): array
     {
@@ -836,8 +836,7 @@ private function objectParam(mixed $value): array
      * @param int $typeAnnotation The type annotation code
      * @param array $nestedDefinition [optional] A nested definition, to define
      *        the structure of an array or struct type.
-     * @param string $nestedDefinitionType [optional] Either `arrayElementType`
-     *        or `structType`.
+     * @param 'arrayElementType'|'structType'|null $nestedDefinitionType
      * @return array{
      *     code?: int,
      *     arrayElementType?: array,